The present invention relates generally to systems for limiting the rotational speed of a turbocharger coupled to an internal combustion engine, and more specifically to such systems operable to limit turbocharger speed by limiting fueling under specified conditions.
In many internal combustion engine applications including a turbocharger, systems are known for limiting turbocharger rotational speed to prevent premature turbocharger damage and/or wear. It is desirable in some such applications to limit turbocharger rotational speed under normal engine operating conditions, but to also allow for increased turbocharger rotational speed and attendant increased engine performance when a bonafide need for increased engine performance exists.
The present invention comprises one or more of the following features or combinations thereof. A system for limiting rotational speed of a turbocharger coupled to an internal combustion engine. The system may include a fuel system responsive to a fueling signal to supply fuel to the engine and a controller determining a fueling command that is air-to-fuel or oxygen-to-fuel control (AFC/OFC) limited under certain engine operating conditions and is otherwise not AFC/OFC limited, wherein the controller produces the fueling signal as a function of the fueling command and also limits the fueling signal according to a turbocharger speed fuel limit in a manner that limits the rotational speed of the turbocharger to a first turbocharger speed limit whenever the fueling command is AFC/OFC limited. The controller may further remove the turbocharger speed fuel limit from the fueling signal when the change in the engine operating parameter exceeds a threshold value and the fueling command is thereafter no longer AFC/OFC limited.
The engine operating parameter may be any one or combination of engine acceleration, driver requested torque, turbocharger boost pressure, engine load, engine fueling, or the like.
The controller may further include a delay value stored therein, wherein the controller is operable to remove the turbocharger speed fuel limit from the fueling signal upon expiration of a time period defined by the delay value following the change in the engine operating parameter exceeding the threshold value and the fueling command thereafter no longer being AFC/OFC limited.
The controller may further include a transition rate value stored therein, wherein the controller is operable to remove the turbocharger speed fuel limit from the fueling signal at a rate defined by the transition rate value.
The controller may further include a fueling command determination strategy operable to determine the fueling command as a function of a number of engine operating condition signals. The fueling command determination strategy may include an AFC/OFC control strategy limiting a maximum value of the fueling command under the certain engine operating conditions, and otherwise not limiting the maximum value of the fueling command.
The controller may further include a final fueling determination strategy producing the fueling signal as a function of at least the fueling command. The controller may further include a number of fuel limiting strategies each providing a fuel limiting value to the final fueling determination strategy, wherein the final fueling determination strategy produce the fueling signal as a function of the fueling command and the number of fuel limiting values. The controller may further include a turbocharger speed fuel limit strategy providing the turbocharger speed fuel limit to the final fueling determination strategy, wherein the final fueling determination strategy limits the fueling signal according to the turbocharger speed fuel limit.
These and other objects of the present invention will become more apparent from the following description of the illustrative embodiments.